Physiological and growth indexes determination
Chlorophyll content in the P. massoniana seedling leaves was
determined referring previous
report.18 Leaf net
photosynthetic rate (Pn) was measured with a portable photosynthesis
system (Li-6400, Li-Cor, Lincoln, NE, USA) following our previous
instrument operation.18At least 10 samples were randomly selected from the seedlings under each
Ca level.
For the measurement of Ca content in the leaves, the leaf tissue were
initially dried at 80°C, then ashed at 550°C and dissolved in
concentrated HNO3 and digested using a microwave
digestion machine (MARS6, CEM, USA). Finally, an ICP-MS based element
analysis was
performed.22
To access the biomass of the seedlings grown at different Ca levels, the
dry weight of seedling were measured. Seedlings were oven-dried (80°C)
to constant weight and measured with an analytical balance.
Soluble protein content were measured referring Qiao et
al.23 Oxidation stress
related parameters, leaves hydrogen peroxide
(H2O2) content, total ascorbate
peroxidase (APX) activity and total superoxide dismutase (SOD) activity
were detected follow previous
procedures.24